A new military alliance is emerging in eastern Europe which will redefine the geopolitical order in the region. It will also mark the emergence of Poland as a major European actor, entrench the position of the US and the UK in European affairs, and marginalise France, Germany and the EU.

This is being driven by the increased threat from Russia and the desire of the eastern Europeans for security, the reluctance of the western Europeans to confront their eastern foe, the consequent necessity for the eastern Europeans to find ways to protect themselves, and the external support of the United States and Britain, which want the region to provide for its own security.

The idea of a regional alliance is actually nothing new, although events over the last 200 years have continually conspired against it.

For much of the early modern period, Poland led an alliance of peoples extending from the Baltic to the Black Sea – including modern-day Estonians, Latvians, Lithuanians, Belarussians and Ukrainians – as part of the Polish-Lithuanian Commonwealth. This served to contain the threat from Russia, which began to expand out of its core in Muscovy in the sixteenth and seventeenth centuries.

The Polish-led alliance eventually collapsed in the late eighteenth century, weakened by internal disputes and the growing strength of Russia, which consequently captured the territory of modern Ukraine, Belarus and eastern Poland, including Warsaw, where the Russians remained until 1917.

With Russia’s defeat in the First World War, and later that of Germany and Austria, Poland was able to re-establish its independence. To ensure its survival, it called for an alliance of the newly formed states in its neighbourhood, a so-called Intermarium – in Latin, between the seas – which could withstand the irredentist ambitions of their larger neighbours.

However, this initiative never gained traction. A resurgent Russia reconquered White Russia, and Ukraine in the early 1920s, and the other countries in the region – the Baltic states of Estonia, Latvia and Lithuania, plus Czechoslovakia, Hungary and Romania – were either too weak, too divided or too suspicious of Poland to want to form a regional alliance.

Meanwhile, the US and UK, potential sponsors of such an alliance, were largely absent, with the former retreating to the other side of the Atlantic before entering the Depression and the latter focused on maintaining its empire.

Consequently, Russia was able to reimpose itself on the region in the 1940s, starting with the division of Poland by agreement with Germany, and subsequently by conquest, as the Red Army rolled westwards to Berlin following the battle of Stalingrad, and occupying the lands along the way.

Russian domination was formalised by agreement with the US and UK at Yalta in 1945, and the captive states welded into a regional military alliance, the Warsaw Pact, ten years later, with the aim of deterring a prospective attack from NATO.

This arrangement collapsed at the end of the Cold War era, as the Soviet Union entered into terminal decline and the US and UK demanded that it relinquish its outer empire in eastern Europe. However, the various states of the region did not attempt to form any kind of new military or political alliance, despite their continued fear of Russia’s return.

Instead, most countries focused on joining NATO, supported by the US and UK, which were to breathe new life into the organisation following the end of the Cold War, and the acquiescence of the western Europeans at a point where Russia was weak and the Article V security guarantee was largely theoretical.

Meanwhile, Ukraine and Belarus remained under Russian suzerainty, notionally independent following the break-up of the Soviet Union but practically beholden to Moscow and unable to enter into any kind of alliance with their neighbours to the west.

If the story of the last 200 years has been about the region’s failure to coalesce into any sort of alliance, the events of the last few years – and especially since February last year – mark the opening of a new and distinctive chapter.

As before, Russia continues to threaten the region, having regained some of its strength since the collapse of the Soviet Union and a determination to maintain a sphere of influence in eastern Europe, with its full extent to be defined.

It has resisted attempts by former Soviet states in its near abroad to escape Russia’s orbit, most notably Ukraine, successfully supressing the Orange Revolution of 2004, invading the Donbas and annexing Crimea following the Maidan Revolution of 2013, and attacking the rest of the country last February. It also insisted on maintaining a dominant position in Belarus via its pliant leader, Aleksandr Lukashenka.

Unsurprisingly, the effect has been to galvanise opposition to Russia in these subject countries, which are more determined than ever to break free and to unnerve the peoples residing immediately to their west – especially in Poland and the Baltic, who fear that once Russia has established its control of its first tier of buffers, they will be next in line.

In a previous era, their inclination was to look solely to NATO to protect them from any potential attack from Russia – and, in large measure, they still do. However, more recently, this impulse has been accompanied by growing doubts about the commitment of the western Europeans in guaranteeing the security of eastern Europe, given their apparent desire for good relations with Russia, their growing dependence on its energy, their reluctance to spend money on defence, as well as the pacifist inclinations of elites in countries such as Germany and Luxembourg, and their antagonism towards countries such as Poland for alleged breaches of the rule of law.

These doubts have only been confirmed by the reaction of western Europeans to the crisis in Ukraine, which has been characterised by a conspicuous ambivalence, despite the evident threat it poses to other states on Russia’s frontline.

Germany has been reluctant to send weapons, France has called repeatedly for a compromise in which Ukraine cedes territory to Russia, Austria and Italy have called for an end to sanctions, and Hungary, which has chosen to align with western Europe, has blocked financial assistance to Ukraine. Ukrainians have viewed their behaviour with a mixture of anger, disappointment and weary fatalism.

The question for the eastern Europeans now is whether they can really rely on their western counterparts to come to their defence, having seemingly failed Ukraine during its hour of need. Ukraine may not be a member of NATO, but what does western Europeans’ reluctance to confront Russia say about their commitment to its immediate neighbours? How much blood and treasure would they expend if Russia invaded the Baltic states?

At the same time that western Europeans reveal their ambivalence, the US and the UK have been intensifying their steps to weld the eastern Europeans into a new alliance outside the framework of NATO.

Officials in Washington have called explicitly for the creation of a new political and military alliance comprising Poland, Ukraine, Estonia, Latvia, Lithuania and the UK, while London itself has signed a succession of defence treaties with the region, most notably a trilateral security pact with Poland and Ukraine in February last year, just prior to Russia’s invasion.

This was followed in May by calls from the then prime minister, Boris Johnson, for the creation of a new ‘European Commonwealth’ along the lines suggested by the US, comprising Britain, Poland, Ukraine and the three Baltic states.

In the meantime, both the Americans and British have provided practical support for the security of the region, within the framework of NATO where possible and outside its framework when necessary.

The US has deployed thousands of troops and heavy weapons to frontline states in eastern Europe, sold heavy weaponry, including missiles, tanks and fighter planes to the region, and the Patriot air and missile defence system to Poland – which it has declared to be its most important partner in continental Europe – and announced the creation of a permanent military base in Poznań for the US Fifth Army Corps.

The UK has similarly led NATO’s forward mission in Estonia and provided Ukraine with heavy weaponry, most recently agreeing to donate it 14 Challenger tanks. To bypass German opposition, it has avoided transporting this weaponry via German airspace – and publicly drawn attention to this point.

These actions are underpinned by a basic alignment of interests with the eastern Europeans in seeking to push back against Russia. The US has seen the invasion of Ukraine as an opportunity to knock Russia out of the ranks of the Great Powers and subordinate it to the West, leaving Washington free to focus on what it sees as its emerging confrontation with China.

Meanwhile, the UK has acted out of a strategic interest in aligning with the US, solidarity with the Baltic peoples, a long-standing suspicion of Russia, and a desire to punish Moscow for years of malfeasance, including various poisonings on British soil. This has been made possible by the opportunity of a more independent foreign policy following Brexit.

The proviso is a reluctance by the US and UK to provoke Russia too severely or commit their own troops to any potential combat. Despite its intervention in eastern Europe, the former remains focused primarily on China and is naturally wary of Russia which, despite its weaknesses, retains nuclear weapons and clear red lines. Britain, the junior partner to the US, is constrained by a lack of service personnel. Both face public opposition at home.

Conspicuously, the US has so far refused to provide fighter planes or tanks to Ukraine, and there has been no discussion of establishing bases or deploying boots on the ground. On the contrary, officials have gone to lengths to assure Russia that the Fifth Army Corps are not combat troops.

Instead, their preference is for the eastern Europeans themselves to take responsibility for their own security, for which the US and the UK will provide the necessary logistical and political support to break down the barriers to regional cooperation.

Put together, the combination of Russian threat, western European passivity and Anglo-American support has begun to change the dynamics in eastern Europe which are now coalescing into a coherent regional alliance, operating both within and outside NATO.

A belt of states, stretching from Estonia to Bulgaria, has formed an organisation known as the Bucharest Nine which seeks to co-ordinate security policy and mobilise external support, underpinned by intensified bilateral and regional contacts and the establishment of the Three Seas Initiative, which provides it with a political and economic underpinning.

They have deployed troops to each other’s countries as part of NATO’s forward mission in eastern Europe – Czechs, Poles and Slovaks to Latvia; Romanians to Poland; and Slovenes and Czechs to Slovakia – and reiterated their collective security guarantee to one another.

More recently, they have also sought to bring Ukraine under their security umbrella. Poland and Lithuania have established a formal security pact with Ukraine – the Lublin Triangle – and created a joint military brigade. The region has donated lethal weaponry to the country, in some cases via their common border.

With the exception of Hungary, eastern Europeans have also provided emphatic political support for Ukraine, involving calls for NATO to supply it with weaponry, sanctuary for refugees, and repeated expressions of fraternity with the Ukrainian people.

At the centre of all these efforts is Poland, the most populous state in the region, with the largest economy and the best equipped army. It has explicitly revived the concept of an Intermarium that gathers up its neighbours in a new regional alliance.

Where this goes next remains a matter of informed speculation. It seems unlikely that the threat from Russia will recede, even if a victory in the war is now improbable, given its poor performance so far on the battlefield.

Russia’s existential investment in the future of Ukraine means it will not withdraw from the fight and it continues to enjoy the support of the local population in eastern Ukraine. Accordingly, a central scenario involves a victory by Ukraine but an inconclusive one, in which Russia retreats but retains control of Donbas, remains a threat to the rest of Ukraine and, in the view of its neighbours, a latent threat to themselves.

The western Europeans are likely to retain an ambivalent position towards Russia and the security of eastern Europe, and especially towards Ukraine, whose membership of NATO will be denied. A lack of solidarity, and fears about the impact on a fragile EU, will also rule out any chance of Ukraine enjoying the soft security of EU membership.

Instead, the most the western Europeans will offer is financial support for reconstruction and development – although perhaps not very much, given fears of corruption and the misappropriation of funds, and the attachment of onerous conditions intended to bring Ukraine under the EU’s legal order.

By contrast, the US and Britain will continue to support the integration of the region, in which they will retain a strategic interest. Certainly, this will include direct aid to Ukraine itself in the form of weaponry and military assistance, as happened before the war.

However, this will be accompanied by a continued wariness of Russia, the delegation of responsibility for upholding Ukraine’s physical security and wellbeing to its neighbours, and political, financial and military sponsorship of Poland, which Washington and London will expect to play the leading role.

As for Poland itself, the evidence suggests it is already warming up for just such a task, with plans to raise defence spending to as much as five per cent of GDP, involving massive arms purchases, the establishment of its own military-industrial complex and the expansion of its army to 300,000 – by far the largest in Europe, except for Ukraine.

It is a scenario involving various elements. Ukraine will continue to seek security from external partners, above all the US and the UK, but by default, its immediate neighbourhood and Poland, which will share its anxieties about Russia’s propensity for future aggression.

This will require a high degree of organisation, especially if regional states follow the logic of their position and deploy peacekeeping troops to Ukraine – the best form of deterrence and one which Poland will be capable of performing. However, this is unlikely to happen under a NATO banner because of the objections of the western Europeans and the wariness of the US to crossing what is likely to be a red line for Russia.

Consequently, there will be a need for the establishment of a formal pact among the participating nations, building on existing agreements within the region and outside the framework of NATO, and enshrined in the form of a treaty.

As in the Cold War era, the core purpose of this pact will be the security of eastern Europe and Ukraine against the risk of external attack. The difference this time is that it will be organised and sponsored by the US and the UK rather than Russia, and intended to deter an attack from the east rather than the west. In short, a new Warsaw Pact, updated for the circumstances of the twenty-first century.

Any such scenario would inevitably imply a profound redefinition of politics in eastern Europe and beyond. It would mark the emergence of Poland as a major European actor, with a hegemonic position in its immediate neighbourhood, and a new international vocation in the reconstruction and integration of Ukraine – and perhaps also Belarus if the Lukashenka government falls in the wake of Russia’s retreat.

It would mark the formation of a new entity in eastern Europe, based on a close alliance between Poland and Ukraine, with a combined population of 80 million, and a set of smaller members adding tens of millions more. Under Polish leadership, this could form the basis of a broader political and economic alliance in line with its ambition to establish a new Intermarium.

It would entrench the position of the US and the UK in European affairs, putting paid to the idea that Britain has abandoned Europe in the wake of Brexit, and the ambitions of some in western Europe to establish the EU as a strategically autonomous actor.  On the contrary, a new alliance in eastern Europe, dedicated to its own security needs, would marginalise France and Germany, threaten the predominant position of the EU in Europe and galvanise its seeming slow-motion decline.

After a hiatus of more than 200 years, a formal alliance between the peoples of eastern Europe may once again be in sight and, as a product of this, an epochal change in the European geopolitical order as we know it.